Piezoelectric element and liquid jet head using the piezoelectric element

ABSTRACT

Provided are a piezoelectric element and a liquid-jet head using the same, in which favorable crystallinity can be obtained with improved uniformity, breakage of a piezoelectric film can be prevented, thereby providing stable displacement properties. The piezoeletric element includes a lower electrode, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film. The piezoelectric film in turn includes a lower layer portion having column crystals, and an upper layer portion having column crystals which are continuous from those in the lower layer portion and having sizes larger than those in the lower layer portion.

This is a National Stage entry Application based on PCT/JP2003/007990,filed on Jun. 24, 2003. The entire disclosure of the prior application,application number PCT/JP2003/007990, is considered part of thedisclosure of the present application and is hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a piezoelectric element and a liquidjet head using the same, and particularly to a manufacturing method ofthe piezoelectric element, which can make a crystal orientation within awafer surface uniform, thus making piezoelectric properties of thepiezoelectric element uniform.

BACKGROUND ART

A piezoelectric element is an element in which a piezoelectric film,having an electromechanical transducing function, is sandwiched by twoelectrodes. The piezoelectric film is made of crystallized piezoelectricceramics.

Conventionally, a so-called sol-gel method has been known as amanufacturing method of the piezoelectric element. Specifically, a solof an organometallic compound is applied on a substrate in which a lowerelectrode is formed, and then the sol is dried and degreased to form aprecursor film of a piezoelectric layer. After the steps of application,drying and degreasing of the sol is carried out predetermined times, thesol is subject to heat treatment at high temperature to be crystallized.In order to increase the thickness of the layer, the steps ofapplication, drying and degreasing, as well as the step of crystallizingthe sol are further carried out on the crystallized piezoelectric layerrepeatedly.

A degreasing method using a tray dryer or a hot plate is known as amethod of degreasing the above mentioned sol of the organometalliccompound.

Further, this type of piezoelectric element is applied to a liquid jethead such as an ink-jet recording head. In the ink-jet recording head, avibration plate constructs a part of each pressure generating chamberwhich communicates with a nozzle orifice for ejecting ink, and thevibration plate is deformed by the piezoelectric element to pressurizeink within the pressure generating chamber and thereby the ink dropletsare ejected from the nozzle orifice. There are two types of ink-jetrecording heads which are in practical use: the ink-jet recording headusing a piezoelectric actuator in a longitudinal vibration mode wherethe actuator stretches and shrinks in an axis direction of thepiezoelectric element; and the ink-jet recording head in a flexuralvibration mode. The ink-jet recording head in the flexural vibrationmode is typified by a known ink-jet recording head in which thepiezoelectric elements are formed in the following manner: a uniformpiezoelectric layer is formed over the entire surface of the vibrationplate by a deposition technology; and the piezoelectric layer thusobtained is cut using a lithography method into pieces, each having ashape corresponding to each pressure generating chamber so that thepiezoelectric elements are formed separately for the respective pressuregenerating chambers.

There is an example of the ink-jet recording head having theaforementioned piezoelectric element in the flexure vibration mode,which is disclosed in Japanese Patent Laid-Open Publication No.2000-326503. In this ink-jet recording head, a lower electrode whichconstitutes the piezoelectric element is patterned in a region facingthe pressure generating chamber, thus suppressing initial flexure of thevibration plate and increasing an amount of displacement of thevibration plate due to drive of the piezoelectric element.

In the conventional degreasing step in manufacturing the piezoelectricelement, nucleuses of piezoelectric crystals in the precursor of thepiezoelectric film has not been easily formed. Therefore, it has beendifficult to obtain desired crystals when the precursor is crystallized.Moreover, degreasing conditions have varied due to, for example,variations in a rate of temperature increase depending on a positionwithin the wafer surface. This could result in variations in crystalorientations and piezoelectric properties.

Moreover, when forming the piezoelectric film on the lower electrodewhich is patterned as mentioned earlier, a problem arises that portionsof the piezoelectric film formed to cover edges of the lower electrodeand other portion of the same formed on the outer sides of the lowerelectrode have poor film qualities, and thereby a drive reliability ofthe piezoelectric element is degraded. In other words, the piezoelectricfilm on the lower electrode and the same on the outer sides of the lowerelectrode have different properties of crystals and the like. Thus, thepiezoelectric layer is substantially discontinuous in the vicinities ofedges of the lower electrode thereby causing breakage such as a crack inthe piezoelectric film when a voltage is applied thereto. This breakageeasily happens particularly in the piezoelectric film in the regioncorresponding to the edges of the lower electrode in a longitudinaldirection thereof.

DISCLOSURE OF THE INVENTION

In consideration of the foregoing circumstances, it is an object of thepresent invention to provide a piezoelectric element in which desiredand favorable crystallinity is obtained with improved uniformity thereofand breakage of a piezoelectric film is prevented to obtain stabledisplacement properties, a liquid jet head using the piezoelectricelement, and a manufacturing method thereof.

The first aspect of the present invention for solving the aforementionedproblems is a manufacturing method of a piezoelectric element includingthe steps of forming a lower electrode on a substrate, forming apiezoelectric film on the lower electrode, and forming an upperelectrode on the piezoelectric film. In the step of forming thepiezoelectric film, steps of forming a piezoelectric layer are carriedout a plurality of times, whereby a plurality of the piezoelectriclayers are stacked, the steps of forming the piezoelectric layerincluding applying a sol containing an organometallic compound, dryingthe sol containing the organometallic compound, degreasing the solcontaining the organometallic compound so that the sol is gelated, andcrystallizing the gelated organometallic compound. Moreover, whenforming a lowermost layer of the piezoelectric layers, a rate oftemperature increase during at least initial degreasing thereof is setto 500° C./min or lower.

In the first aspect, when the lowermost layer of the piezoelectriclayers is formed, the rate of temperature increase while degreasing ismaintained relatively low, thus forming a number of small seed crystalswithin the lowermost layer of the piezoelectric layers. Thus, thepiezoelectric film with a favorable film quality can be formed.

The second aspect of the present invention is characterized by that, inthe manufacturing method of a piezoelectric element according to thefirst aspect, when forming at least one layer of the piezoelectriclayers except for the lowermost layer, the rate of temperature increaseduring degreasing thereof is set to be 1000° C./min or higher.

In the second aspect, crystals grow from the nucleuses of piezoelectriccrystals which are previously crystallized. Therefore, the crystals ofthe piezoelectric film are prevented from being discontinuous.

In the third aspect of the present invention, a manufacturing method ofa piezoelectric element includes the steps of forming a lower electrodeon a substrate, forming a piezoelectric film on the lower electrode, andforming an upper electrode on the piezoelectric film. In the step offorming the piezoelectric film, steps of forming a piezoelectric layerare carried out a plurality of times, whereby a plurality of thepiezoelectric layers are stacked, the steps of forming the piezoelectriclayer including applying a sol containing an organometallic compound,drying the sol containing the organometallic compound, degreasing thesol containing the organometallic compound so that the sol is gelated,and crystallizing the gelated organometallic compound, When forming alowermost layer of the piezoelectric layers, a rate of temperatureincrease during at least initial degreasing thereof is set to be equalto or lower than that during degreasing of the other piezoelectriclayers.

In the third aspect, when the lowermost layer of the piezoelectriclayers is formed, the rate of temperature increase while degreasing ismaintained low, thus forming a number of small seed crystals within thelowermost layer of the piezoelectric layers. Thus, the piezoelectricfilm with a favorable film quality can be formed.

The fourth aspect of the present invention is a manufacturing method ofa piezoelectric element according to the third aspect of the presentinvention in which, the step of forming the piezoelectric film includes:forming a first piezoelectric layer, which is the lowermost layer of thepiezoelectric layers, on the lower electrode provided over an almostentire surface of the substrate; patterning the lower electrode and thefirst piezoelectric layer to have a predetermined shape; and forminganother piezoelectric layer to cover end surfaces of the lower electrodeand the first piezoelectric layer. The rate of temperature increaseduring degreasing for forming the first piezoelectric layer and a secondpiezoelectric layer provided immediately on the first piezoelectriclayer is set to be equal to or lower than that during degreasing forforming the rest of piezoelectric layers.

In the fourth aspect, the film quality of the piezoelectric film,especially of the piezoelectric film on edges and outer sides of thelower electrode, is improved.

The fifth aspect of the present invention is a manufacturing method of apiezoelectric element according to the fourth aspect of the presentinvention, in which each of the first and second piezoelectric layersare formed by applying a sol containing the organometallic compoundonce, followed by gelation and crystallizing the sol, and the rest ofthe piezoelectric layers are formed by applying the sol containing theorganometallic compound twice or more, followed by gelation andcrystallization of the sol.

In the fifth aspect, the film quality of the piezoelectric film isimproved, and efficiency in manufacturing the same is also improved.

The sixth aspect of the present invention is a manufacturing method of apiezoelectric element according to any one of fourth and fifth aspectsof the present invention, in which after the lower electrode and thefirst piezoelectric layers are patterned, crystal seeds which becomenucleuses of the piezoelectric film are continuously formed from thefirst piezoelectric layer through outer sides thereof.

In the sixth aspect, the second piezoelectric layer has a crystalstructure which orients in one direction by virtue of the crystal seedsand is thus formed approximately uniformly. Therefore, the film qualityof the piezoelectric film is surely improved.

The seventh aspect of the present invention is a manufacturing method ofa piezoelectric element according to any one of fourth to sixth aspectof the present invention, in which the lower electrode and the firstpiezoelectric layer are patterned by ion milling.

In the seventh aspect, the lower electrode and the first piezoelectriclayer can be patterned to have a desired shape relatively easily.

The eighth aspect of the present invention is a manufacturing method ofa piezoelectric element, including the steps of forming a lowerelectrode on a substrate, forming a piezoelectric film on the lowerelectrode, and forming an upper electrode on the piezoelectric film. Inthe step of forming the piezoelectric film, steps of forming apiezoelectric layer are carried out a plurality of times, whereby aplurality of the piezoelectric layers are stacked, the steps of formingthe piezoelectric layer including applying a sol containing anorganometallic compound, drying the sol containing the organometalliccompound, degreasing the sol containing the organometallic compound sothat the sol is gelated, and crystallizing the gelated organometalliccompound. The rate of temperature increase during degreasing of at leastthe piezoelectric layer formed by initial crystallizing is set to beequal to or lower than that during degreasing for the rest ofpiezoelectric layers formed by following crystallization.

In the eighth aspect, when forming a lower layer of the piezoelectriclayers, the rate of temperature increase while degreasing is maintainedrelatively low, thus forming a number of small seed crystals within thepiezoelectric layer. Consequently, the piezoelectric film with afavorable film quality can be formed.

The ninth aspect of the present invention is a manufacturing method of apiezoelectric method according to any one of first to eighth aspects inwhich when the degreasing is performed, the sol is heated from a side ofthe substrate.

In the ninth aspect, heating can be performed under relatively uniformtemperature conditions, making it possible to perform uniform andefficient degreasing.

The tenth aspect of the present invention is a manufacturing method of aliquid jet head, in which a piezoelectric element made in themanufacturing method of any one of the first to ninth aspects is used.

In the tenth aspect, since ejection properties are improved and alsobecome uniform, the liquid-jet head with improved reliability isrealized relatively easily.

The eleventh aspect of the present invention is a piezoelectric elementwhich includes a lower electrode, a piezoelectric film formed on thelower electrode, and an upper electrode formed on the piezoelectricfilm. The piezoelectric film includes a lower layer portion havingcolumn crystals, and an upper layer portion having column crystals whichare continuous from those in the lower layer portion and have sizeslarger than those in the lower layer portion.

In the eleventh aspect, the film quality of the piezoelectric film, suchas crystallinity thereof, is improved and also becomes uniform.

The twelfth aspect of the present invention is a piezoelectric elementaccording to the eleventh aspect of the present invention, in which thelower electrode is patterned to have a predetermined shape, a firstpiezoelectric layer, which is a lowermost layer of a plurality ofpiezoelectric layers constructing the piezoelectric film, is formed onlyon the lower electrode, and the rest of the piezoelectric layers areformed, covering end faces of the lower electrode and the firstpiezoelectric layer. The first piezoelectric layer and a secondpiezoelectric layer are formed directly on the first piezoelectric layerconstruct the lower layer portion.

In the twelfth aspect, the film quality of the piezoelectric film, suchas crystallinity thereof, is improved. Particularly, the film quality ofthe piezoelectric film on end faces and the outer sides of the lowerelectrode is improved and thereby favorable piezoelectric properties canbe obtained.

The thirteenth aspect of the present invention is a piezoelectricelement according to the twelfth aspect of the present invention, inwhich a thickness of each of the first and second piezoelectric layersis thinner than that of each of the rest of the piezoelectric layers.

In the thirteenth aspect, the film quality of the piezoelectric film ismore surely improved.

The fourteenth aspect of the present invention is a piezoelectricelement according to any one of the twelfth and the thirteenth aspectsof the present invention, in which the end faces of the lower electrodeand the first piezoelectric layer are inclined at a predetermined anglewith respect to surfaces thereof.

In the fourteenth aspect, the film qualities of the second piezoelectriclayer and the like formed immediately on the lower electrode and thefirst piezoelectric layer are improved, thus preventing a crack or thelike in the piezoelectric film by voltage application.

The fifteenth aspect of the present invention is a piezoelectric elementaccording to any one of twelfth to fourteenth aspects of the presentinvention, in which metallic layers, which are electrically disconnectedfrom the lower electrode, are provided in vicinities of edges of thepiezoelectric film.

In the fifteenth aspect, the piezoelectric layer is formed by beingcrystallized under approximately uniform heating conditions, and therebythe piezoelectric film with favorable film quality can be obtained.

The sixteenth aspect of the present invention is a liquid-jet head,including the piezoelectric element according to any one of eleventh tofifteenth aspects of the present invention as a driving source of liquidejection.

In the sixteenth aspect, ejection properties are improved and alsobecome uniform, thus realizing the liquid jet head with improvedreliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a construction of a printer accordingto Embodiment 1.

FIG. 2 is an exploded perspective view schematically showing a recordinghead according to Embodiment 1.

FIGS. 3( a) and 3(b) are a plan view and a cross-sectional view,respectively, of the recording head according to Embodiment 1.

FIG. 4 is a schematic cross-sectional view showing a layer constructionof a piezoelectric element according to Embodiment 1.

FIGS. 5( a) to 5(f) are cross-sectional views of the recording head,showing manufacturing steps thereof according to Embodiment 1.

FIGS. 6( a) to 6(d) are cross-sectional views of the recording head,showing manufacturing steps thereof according to Embodiment 1.

FIG. 7 is a partial cross-sectional view showing details of a layerconstruction of the piezoelectric element.

FIG. 8 is an exploded perspective view showing a recording headaccording to Embodiment 2.

FIGS. 9( a) and 9(b) are a plan view and a cross-sectional view,respectively, of the recording head according to Embodiment 2.

FIG. 10 is a cross-sectional view of the recording head according toEmbodiment 2.

FIGS. 11( a) to 11(c) are cross-sectional views of the recording head,showing manufacturing steps thereof according to Embodiment 2.

FIGS. 12( a) to 12(c) are cross-sectional views of the recording head,showing manufacturing steps thereof according to Embodiment 2.

FIGS. 13( a) to 13(c) are cross-sectional views of the recording head,showing manufacturing steps thereof according to Embodiment 2.

FIGS. 14( a) and 14(b) are cross-sectional views of the recording head,showing manufacturing method thereof according to Embodiment 2.

FIGS. 15( a) and 15(b) are cross-sectional views of the recording head,showing manufacturing method thereof according to Embodiment 2.

FIGS. 16( a) and 16(b) are a plan view and a cross-sectional view,respectively, of a recording head according to Embodiment 3.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

Embodiments of the present invention will be described below withreference to the drawings.

Embodiment 1

FIG. 1 is an explanatory view of a construction of a printer (an exampleof a liquid jet device) using an ink-jet recording head (an example of aliquid jet head) which is provided with a piezoelectric elementmanufactured in a method of this embodiment. This printer is providedwith a body 2, a tray 3, a discharge port 4 and an operation panel 9. Inaddition, the ink-jet recording head 1, a feeding mechanism 6 and acontrol circuit 8 are provided within the body 2.

The ink-jet recording head 1 is provided with the piezoelectric elementmanufactured in the manufacturing method of the present invention. Theink-jet recording head 1 is constructed to be able to eject ink, whichis a liquid, from a nozzle in accordance with an ejection signalsupplied from the control circuit 8.

The body 2 is a casing of the printer, in which the feeding mechanism 6is placed at the position where paper 5 can be fed from the tray 3, andthe ink-jet recording head 1 is placed to be able to print the paper 5.The tray 3 is constructed so that the paper 5 before being printed canbe fed into the feeding mechanism 6. The discharge port 4 is an exitwhere the paper 5 after being printed is discharged.

The feeding mechanism 6 is provided with a motor 600, rollers 601 and602, and other unillustrated mechanical construction. The motor 600 canrotate in accordance with the drive signal supplied by the controlcircuit 8. The mechanical construction is configured to be able totransfer rotation force of the motor 600 to the rollers 601 and 602. Therollers 601 and 602 rotate when the rotation force of the motor 600 istransferred thereto. The paper 5 put on the tray 3 is then drawn by therotation of the motors 601 and 602 and fed to be printed by the head 1.

The control circuit 8 is provided with a CPU, a ROM, a RAM, an interfacecircuit and the like, which are not shown. The control circuit 8 cansupply a drive signal and an ejection signal to the feeding mechanism 6and the ink-jet recording head 1, respectively, in accordance withprinting information supplied by a computer through an unillustratedconnector. In addition, the control circuit 8 can set an operation modeand perform reset processing and the like in accordance with anoperation signal from the operation panel 9.

Next, a construction of the ink-jet recording head mounted on this typeof printer is described. FIG. 2 is an exploded perspective viewschematically showing the ink-jet recording head according to Embodiment1 of the present invention. FIG. 3( a) is a plan view of FIG. 2 and FIG.3( b) is a cross-sectional view taken along the like A-A′. FIG. 4 is aschematic cross-sectional view showing a layer construction of thepiezoelectric element.

As illustrated, a passage-forming substrate 10 in this embodiment ismade of a single crystal silicon substrate with a plane orientation(110). On one side of the passage-forming substrate 10, an elastic film50 is formed. The elastic film 50 has a thickness of 1 to 2 μm and ismade of silicon dioxide which is previously formed by thermaloxidization. In the passage-forming substrate 10, a plurality ofpressure generating chambers 12 are arrayed side by side in a widthdirection of the pressure generating chamber 12. In addition, acommunicating portion 13 is formed in the passage-forming substrate 10in a longitudinal outer region of the pressure generating chambers 12.The communicating portion 13 and each of the pressure-generatingchambers 12 communicate with each other through ink supply paths 14,respectively. Note that the communicating portion 13 communicates with areservoir portion 31 of a later described reservoir forming plate 30,constructing a part of a reservoir 100 which is a common ink chamber foreach of the pressure generating chambers 12. Each of the ink supplypaths 14 is formed to have a narrower width than that of each of thepressure generating chambers 12, thereby maintaining uniform flowresistance of the ink flown into the pressure generating chamber 12 fromthe communicating portion 13.

Note that it is preferred to select an appropriate thickness of thepassage-forming substrate 10 in which the pressure generating chambers12 and the like are formed, depending on density of pressure generatingchambers 12 provided therein. For example, in the case of arraying about180 pressure generating chambers 12 per inch (180 dpi), the thickness ofthe passage-forming substrate 10 is preferably set to about 180 to 280μm, and more preferably about 220 μm. Moreover, in the case of arrayingthe pressure generating chambers 12, for example, as relatively denselyas about 360 dpi, the thickness of the passage-forming substrate 10 ispreferably set to 100 μm or smaller. This is because the array densityof the pressure generating chambers 12 can be increased whilemaintaining rigidity of the compartment walls 11 between the pressuregenerating chambers 12 neighboring each other.

Moreover, a nozzle plate 20 having nozzle orifices 21 drilledtherethrough is fixed to the open face side of the passage-formingsubstrate 10 through an adhesive, a thermowelding film or the like.These nozzle orifices 21 communicate with the vicinities of ends of thepressure-generating chambers 12 on the opposite side of the ink supplypaths 14. Note that the nozzle plate 20 has a thickness of, for example,0.1 to 1 mm and made of glass ceramics, a single crystal siliconsubstrate, stainless steel, or the like whose coefficient of linearexpansion is, for example, 2.5 to 4.5 [×10⁻⁶/C.°] at temperature of300C.° or lower.

Meanwhile, as shown in FIG. 4, the elastic film 50 with a thickness of,for example, about 1.0 μm is formed on the passage-forming substrate 10on the side opposed to the open face thereof. On the elastic film 50, aninsulation film 55 with a thickness of, for example, about 0.4 μm isformed. On the insulation film 55, a lower electrode film 60 with athickness of, for example, about 0.2 μm, a piezoelectric layer 70 with athickness of, for example, about 1.0 μm and an upper electrode film 80with a thickness of, for example, about 0.05 μm are further stacked in aprocess to be described later, thus configuring each piezoelectricelement 300. Here, the piezoelectric element 300 corresponds to aportion including the lower electrode film 60, the piezoelectric layer70 and the upper electrode film 80. Generally, in each of thepiezoelectric elements 300, any one of the electrodes thereof is used asa common electrode, and the other electrode and the piezoelectric layer70 are patterned for each of the pressure-generating chambers 12.Consequently, here, a portion where piezoelectric strain occurs due tovoltage application to both of the electrodes is called a piezoelectricactive portion, which is configured by any one of the electrodes and thepiezoelectric layer 70 which are patterned. In this embodiment, in eachof the piezoelectric elements 300, the lower electrode film 60 is usedas the common electrode thereof, and the upper electrode film 80 is usedas a separately provided electrode thereof. However, no problem ariseseven when the lower and upper electrodes 80 and 60 are used in the otherway around, for convenience of a drive circuit and wiring. In any ofabove cases, the piezoelectric active portion is formed for each of thepressure generating chambers. Moreover, herein, the piezoelectricelements 300 and the vibration plate displaced by drive of thepiezoelectric elements 300 are collectively called a piezoelectricactuator.

Here, the lower electrode film 60 in this embodiment is formed in thesame region as the insulation film 55 so as to function as the commonelectrode of the plurality of the piezoelectric elements 300 formed onthe passage-forming substrate 10. The lower electrode film 60 also actsas the vibration plate. It is preferred that a material of the lowerelectrode film 60 be a conductive material, for example, platinum,iridium and the like. This is because the piezoelectric film 70,deposited by a spattering or sol-gel method described later, needs to bebaked for crystallization at a temperature from about 600 to 1000° C. inan atmosphere of air or oxygen.

Moreover, the composition of the piezoelectric film 70 maybe, forexample, that of piezoelectric ceramics such as lead zirconate titanate(Pb (Zr_(0.56), Ti_(0.44)) O₃: PZT). Alternatively, lead lanthanumtitanate ((Pb, La) TiO₃), lead lanthanum zirconate ((Pb, La) ZrO₃), leadmagnesium niobate-lead zirconate titanate (Pb (Mg, Nb) (Zr, Ti) O₃:PMN-PZT), barium zirconate titanate (Ba (Zr, Ti) O₃: BZT) and the likemay be used. Further, the material of the upper electrode film 80 is notparticularly limited as long as it is conductive. In this embodiment,iridium (Ir), for example, is used for the upper electrode film 80.

The reservoir forming plate 30 having a reservoir portion 31 is joinedonto the passage-forming substrate 10 in which the foregoingpiezoelectric elements 300 are formed. The reservoir portion 31constructs at least a part of the reservoir 100 which is a common inkchamber for each of the pressure generating chambers 12. In addition, acompliance plate 40 which includes a sealing film 41 and a fixed plate42 is joined onto the reservoir forming plate 30. The sealing film 41 ismade of a flexible material with low rigidity and the fixed plate 42 isformed using a hard material such as metal. The fixed plate 42 isentirely removed in a thickness direction thereof in the region facingthe reservoir 100, thus forming an opening portion 43. Consequently, oneside of the reservoir 100 is sealed only by the sealing film 41.

The foregoing ink-jet recording head in this embodiment takes in inkfrom unillustrated external ink supply means and the inside of therecording head, from the reservoir 100 through the nozzle orifices 21,is filled with the ink. Thereafter, in accordance with a recordingsignal from an unillustrated drive circuit, a voltage is applied throughexternal wiring between the lower and upper electrode films 60 and 80,respectively corresponding to the pressure-generating chambers 12. Theelastic film 50, the insulation film 55, the lower electrode film 60 andthe piezoelectric layer 70 are then flexurally deformed. Thus, pressurein each of the pressure-generating chambers 12 is increased and inkdroplets are ejected from the nozzle orifices 21.

Description will be given below regarding a manufacturing method of theforegoing ink-jet recording head according to this embodiment,particularly a manufacturing method of the piezoelectric element, withreference to FIGS. 5( a) to FIG. 7. First of all, as shown in FIG. 5(a), a silicon wafer 110 which acts as the passage-forming substrate 10is thermally oxidized in a diffusion furnace at temperature of 1100° C.to form silicon dioxide films 52 constructing the elastic film 50 and amask film 51, respectively, over both the upper and lower surfaces ofthe silicon wafer 110. Next, as shown in FIG. 5( b), a zirconium (Zr)layer is formed on the elastic film 50 (silicon dioxide film 52) andthen thermally oxidized in a diffusion furnace, for example, attemperature from 500 to 1200° C., thus forming the insulation film 55made of zirconium oxide (ZrO₂) Next, as shown in FIG. 5( c), the lowerelectrode film 60 made of, for example, platinum and iridium is formedon the insulation film 55. In addition, though unillustrated, a crystalseed layer made of titanium or titanium oxide is formed on the lowerelectrode film 60, with a thickness of preferably about 2 to 200 nm andmore preferably 5 nm. The titanium seed layer is formed by, for example,a known DC spattering method. This seed layer is formed to have auniform thickness, but may also be formed to have an island-like shapewhen necessary.

A titanate film or titanate oxide film (contact layer: not shown) havinga thickness of, for example, about 20 nm may be further formed betweenthe lower electrode film 60 and the insulation film 55. Provision of thecontact layer can improve adhesiveness between the insulation film 55and the lower electrode film 60.

Next, as shown in FIG. 5( d), a piezoelectric precursor film 711′ isdeposited on the lower electrode film 60. The piezoelectric precursorfilm 711′ is constructed as an amorphous film which will be crystallizedby the following treatment so as to be a first piezoelectric layer 711.In this embodiment, a PZT precursor film is deposited by the sol-gelmethod.

The sol-gel method is for hydrolyzing a organometallic compound such asmetal alkoxide using a solution system, and polycondensating the same.To be more specific, a solution (sol) 711″ containing organometalliccompound is applied on a substrate and then dried. The organometalliccompound to be used includes alkoxido such as methoxide, ethoxide,propoxide and butoxide of metal which constructs an inorganic oxide, anacetate compound and the like. Mineral salt such as nitrate, oxalate,perchlorate and the like may also be used.

In this embodiment, a mixed solution (sol) of Pb(CH₃COO)₂.3H₂O, Zr(t-OCH₄H₉)₄, Ti(i-OC₃H₇)₄ is prepared as a starting material of the PZTfilm. This mixed solution is applied by spin coating at a speed of 1500rpm to have a thickness of 0.1 μm. At a stage where the solution isapplied, each metal atoms composing PZT are diffused as organometalliccomplex.

After being applied, the solution is dried at certain temperature for acertain period of time, thus the solvent of the sol is evaporated. Thedrying temperature is set to, for example, 150° C. or higher but notexceeding 200° C., and 180° C. is preferred. The drying time is set to,for example, five minutes or longer but not exceeding 15 minutes, about10 minutes of drying is preferred.

After dried, the sol film is degreased at certain temperature for acertain period of time in an atmosphere. Note that degreasing hereinmeans releasing organic components of the sol film, for example, NO₂,CO₂, H₂O and the like. It is preferred that the degreasing temperaturebe in a range from 300° C. or higher but not exceeding 500° C. This isbecause crystallization starts at temperature exceeding this range, andsufficient degreasing cannot be performed at temperature below thisrange. Preferably, the degreasing temperature is set to about 360 to400° C. The degreasing time is set to, for example, five minutes orlonger but not exceeding 90 minutes. This is because, when degreasing isperformed for a period of time longer than the above range,crystallization starts only in the surface of the film withoutcrystallizing inside of the film, and, when decreasing is performed fora period of time shorter than the range, sufficient degreasing cannot beperformed. Preferably, degreasing is performed for about 10 minutes. Dueto the degreasing, organic substances coordinating to metal aredissociated from metal and oxidization combustion reaction occurstherein. Thus, the organic substances are dispersed into air.

For the first degreasing, in other words, the degreasing for forming thefirst piezoelectric layer 711, a rate of temperature increase is set to500° C./min or lower at least for the initial degreasing. By heating thesol film slowly at low rate of temperature increase, degreasingconditions become uniform, and thereby a number of small seed crystalsare formed within the applied sol 711″″. In order to control the rate oftemperature increase to be 500° C./min or lower, the substrate withapplied sol at room temperature is put on, for example, an aluminumplate at room temperature and then put on a hot plate heated to 400° C.Thus, the rate of temperature increase becomes about 430° C./min. Thesurface of the substrate where the sol is applied comes to the oppositeside of the surface of the hot plate where the substrate is mounted.Therefore, heating starts from the substrate side, thereby realizinguniform and efficient degreasing.

The steps of application, drying and degreasing are repeatedpredetermined times, for example, twice, to form the first piezoelectricprecursor film 711′ (FIG. 5( e)) made of two gel layers. In this case,similarly to the initial degreasing step, it is preferred to heat thesol film at the rate of temperature increase of 500° C./min or lower forthe second degreasing step. Note that the steps of application, dryingand degreasing are conducted not only twice, but only once, or threetimes or more.

Next, the first piezoelectric precursor film 711′ obtained in theaforementioned steps is crystallized by heat treatment, forming thefirst piezoelectric layer 711 (FIG. 5( f)). Although sinteringconditions vary depending on a material, the first piezoelectricprecursor film 711′ is heated at 700° C. in an O₂ atmosphere for 30minutes in this embodiment. Heating equipment may be a diffusion furnaceor rapid thermal annealing (RTA) equipment. As a result of thecrystallization, the first piezoelectric layer 711 is formed. Accordingto this embodiment, 80% or more of crystallized PZT exhibits planeorientation (100), and thereby the piezoelectric film having excellentpiezoelectric properties can be formed. In addition, variation withinthe surface of the substrate is small and thus favorable properties canbe obtained in the entire substrate.

Next, steps similar to the above mentioned steps are repeated fivetimes, thereby forming the piezoelectric film 70 with a predeterminedthickness. These steps mentioned above include application, drying,degreasing of the sol that are repeated twice as well as crystallizationthereafter. For example, when a film thickness of the sol which isapplied once is about 0.1 μm, the thickness of the entire piezoelectricfilm 70 is about 1 μm. FIG. 7 is a partial cross-sectional view showingof a detailed layer construction of the piezoelectric element. Aplurality of piezoelectric layers 712 to 715 are stacked on the firstpiezoelectric layer 711 which is formed in the first crystallizationstep.

In degreasing steps conducted after the initial crystallization, therate of temperature increase is set to 1000° C./min or higher. In orderto control the rate of temperature increase of 1000° C./min or higher,the substrate with the applied sol at room temperature is put, forexample, directly on the hot plate heated to 400° C. Thus, the rate oftemperature increase becomes about 25000° C./min.

Since the sol films are heated rapidly at the rate of temperatureincrease higher than that of the initial degreasing, the seed crystalsare not easily formed within the sol films. Since the seed crystals arenot easily formed, crystals grow in the following crystallization stepsfrom previously crystallized piezoelectric crystals serving asnucleuses. This makes it possible to prevent the piezoelectric crystalsfrom being discontinuous between upper and lower layers. As described sofar, the sol films is heated while the rate of temperature increase forthe initial decreasing is set lower than those for the followingdegreasing. Thus, column crystals having small particle sizes are formedin the first piezoelectric layer 711. In the second and followingpiezoelectric layers 712 to 715, column crystals are formed, which arecontinuous from the first piezoelectric layer 711 and have particlesizes larger than that of the first piezoelectric layer 711. Inaddition, according to this embodiment, 80% or more of crystallized PZThas a plane orientation (100) as affected by the layer below. Besides,variations within the surface of the substrate can be reduced.

Next, as shown in FIG. 6( a), the upper electrode film 80 is formed onthe piezoelectric film 70 formed in the aforementioned manner.Specifically, platinum (Pt) is deposited by a spattering method as theupper electrode film 80 to have a thickness of about 0.05 μm.

Next, resist is applied onto the upper electrode film 80 by spin coatingand then patterned by exposure and development along the position wherethe pressure generating chambers 12 should be formed. Using theremaining resist as a mask, the upper electrode film 80 and thepiezoelectric film 70 are etched by ion milling or the like (FIG. 6(b)).

Thereafter, as shown in FIG. 6( c), the pressure generating chambers 12are formed in the passage-forming substrate 10. Specifically, the maskfilm 51 provided on the surface of the passage-forming substrate 10 ispatterned to have a predetermined shape. Using this mask film 51 as anetching mask, the passage-forming substrate 10 is etched to apredetermined depth, in this embodiment, until the passage-formingsubstrate 10 is penetrated, by dry etching using active gas such asparallel plate type ion etching. Thus, the pressure generating chambers12 are formed. Note that remaining portions configure the compartmentwalls 11.

Finally, as shown in FIG. 6( d), the nozzle plate 20 is joined to thepassage-forming substrate 10 using resin or the like. When joining thenozzle plate 20 to the passage-forming substrate 10, the nozzle plate 20is positioned so that the nozzle orifices 21 are located correspondingto the spaces in the pressure generating chambers 12, respectively. Inthe steps described so far, the ink-jet recording head is formed.

Embodiment 2

FIG. 8 is an exploded perspective view schematically showing an ink-jetrecording head according to Embodiment 2 of the present invention. FIGS.9( a) and 9(b) are a plan view of FIG. 8 and a cross-sectional viewtaken along the line B-B′, respectively. FIG. 10 is a schematic viewshowing a layer construction of a piezoelectric element. Note that thesame members as those described in Embodiment 1 are denoted by the samereferential numerals, and duplicated description is thus omitted.

This embodiment is another example of the layer construction of thepiezoelectric element. Specifically, as shown in FIGS. 8 to 10, the alower electrode film 60A constructing the piezoelectric element 300 ispatterned in the vicinities of both edges of each pressure generatingchamber 12 and continuously provided along a direction in which thepressure generating chamber 12 is provided. Moreover, in thisembodiment, each end face of the lower electrode film 60A in a regionfacing each of the pressure generating chambers 12 is inclined at apredetermined angle with respect to the surface of a passage-formingsubstrate 10.

The piezoelectric film 70A is provided independently for each of thepressure generating chambers 12 and is constructed by a plurality oflayers. In this embodiment, these layers are six piezoelectric layers721 to 726 as shown in FIG. 10. A first piezoelectric layer 721, whichis the lowermost layer amongst the six layers, is provided only on thelower electrode film 60A. Additionally, each end faces of the firstpiezoelectric layer 721 has an inclined plane which is continuous fromeach end plane of the lower electrode film 60A. The second to sixthpiezoelectric layers 722 to 726 formed on the first piezoelectric layer721 are provided on the first piezoelectric layer 721 through aninsulation layer 55, covering the inclined planes of the firstpiezoelectric layer 721 and the lower electrode film 60A.

Herein, the first piezoelectric layer 721 and the second piezoelectriclayer 722 which is formed on the first piezoelectric layer 721, areformed to have crystal densities higher than those of the rest of thelayers, third to sixth layers 723 to 726. Specifically, the third tosixth layers 723 to 726 in a higher portion of the piezoelectric film70A are provided with column crystals having larger sizes than those ofthe first and second piezoelectric layers 721 and 722 in a lower portionof the piezoelectric film 70A. Accordingly, orientation and denseness ofcrystals of the respective piezoelectric layers 721 to 726 are improved,and thereby the film quality of the piezoelectric film 70A can beimproved significantly.

Furthermore, it is preferred that the first and second piezoelectriclayers 721 and 722 be formed to be thinner than the rest of the layers,third to sixth piezoelectric layers 723 to 726. For example, in thisembodiment, the first and second piezoelectric layers 721 and 722 areformed with a thickness of about 0.1 μm, respectively, and the third tosixth piezoelectric layers 723 to 726 are formed with a thickness ofabout 0.2 μm, respectively.

Note that, in this embodiment, each upper electrode film 80 provided oneach of the piezoelectric film 70A is connected to a lead electrode 90made of, for example, gold (Au) or the like, extending to the surface ofthe insulation film 55.

In this embodiment, a reservoir forming plate 30 joined to thepassage-forming substrate 10 is provided with a piezoelectric elementholding portion 32 in a region facing the piezoelectric element 300. Thepiezoelectric element holding portion 32 ensures a space which does notinterfere with movement of the piezoelectric elements 300 and is capableof sealing the space. Each of the piezoelectric elements 300 is sealedwithin the piezoelectric element holding portion 32 which is blockedfrom the external environment. In addition, in a region between thereservoir portion 31 and the piezoelectric element holding portion 32 ofthe reservoir forming plate 30A, a through hole 33 is providedpenetrating the reservoir forming plate 30A in a thickness directionthereof. The vicinity of the end of the lead electrode 90 drawn out ofeach of the piezoelectric elements 300 is exposed within the throughhole 33.

Below is a description regarding a manufacturing method of the ink-jetrecording head according to this embodiment, in particular, amanufacturing method of the piezoelectric element. FIGS. 11( a) to 15(b)are cross-sectional views of the ink-jet recording head, showingmanufacturing steps thereof according to this embodiment.

First of all, as shown in FIGS. 11( a) to 11(c), a silicon dioxide film52 which will be an elastic film 50 and a mask film 51, the insulationfilm 55 and the lower electrode film 60A are formed on a silicon wafer110, similarly to Embodiment 1. Next, as shown in FIG. 12( a), crystalseeds (layer) 65 made of titanium or titanium oxide are formed on thelower electrode film 60A. Note that, in this embodiment, the crystalseeds are formed to have island-like shapes. Next, as shown in FIG. 12(b), a piezoelectric precursor film 721′ that is not yet crystallized isdeposited to have a predetermined thickness which is about 0.1 μm inthis embodiment. Note that the piezoelectric precursor film 721′ isformed by a sol-gel method, in other words, by applying a solution (sol)containing an organometallic compound to have a predetermined thickness,followed by drying and degreasing of the solution.

Here, in this embodiment, a rate of temperature increase whiledegreasing the piezoelectric precursor film 721′ is set to be lower thanthose for the third to sixth piezoelectric layers 723 to 726 formed inthe following steps. To be more specific, it is preferred that the rateof temperature increase while degreasing be, for example, about 1.5 to2° C./second when raising temperature from 250 to 300° C. In this way,many crystal nucleuses can be formed in the piezoelectric film 721′,thereby improving orientation and denseness of the first piezoelectriclayer 721 obtained after a burning step described below.

Thereafter, the silicon wafer 110, on which the piezoelectric precursorfilm 721′ is formed, is inserted into a predetermined dispersion furnaceand the piezoelectric precursor film 721′ is burned at high temperatureof about 700° C. to be crystallized. Consequently, the firstpiezoelectric layer 721 is formed as the closest layer to the lowerelectrode film 60A.

Next, the lower electrode film 60A and the first piezoelectric layer 721are simultaneously patterned. Specifically, as shown in FIG. 12( c),resist is applied on the first piezoelectric layer 721, and then exposedand developed using a mask, thus forming a resist film 200 having apredetermined pattern. Here, the resist is formed by, for example,applying negative resist by a spin coating method or the like.Thereafter, the negative resist is exposed, developed and baked using apredetermined mask, thereby forming the resist film 200. As a matter ofcourse, it is possible to use positive resist instead of negativeresist. In addition, in this embodiment, each end face 201 of the resistfilm 200 is formed to incline at a predetermined angle. The inclinationangle of the end face 201 becomes smaller as a post bake is conductedfor a longer period of time. The inclination angle may also becontrolled by excessive exposure.

Thereafter, as shown in FIG. 13( a), the lower electrode film 60A andthe first piezoelectric layer 721 are patterned through the resist film200 by ion milling. At this time, the lower electrode film 60A and thefirst piezoelectric layer 721 are patterned along each of the inclinedend faces 201 of the resist film 200. Thus, end faces of the lowerelectrode film 60A and the first piezoelectric layer 721 are inclined ata predetermined angle to a vibration plate. Since the end faces of thelower electrode film 60A and the first piezoelectric layer 721 areinclined, the rest of piezoelectric layers can be formed with favorablefilm qualities on the first piezoelectric layer 721.

Next, as shown in FIG. 13( b), crystal seeds (layer) 65A are formed overthe entire surface of the silicon wafer 110 including the firstpiezoelectric layer 721. Thereafter, the piezoelectric precursor film722′ is formed by the spin coating method or the like to have apredetermined thickness, which is about 0.1 μm in this embodiment. Thepiezoelectric precursor film 722′ is then dried, degreased and burned,thus forming the second piezoelectric layer 722. Note that it ispreferred that degreasing of the piezoelectric precursor film 722′,which becomes the second piezoelectric layer 722, be conducted with arelatively low rate of temperature increase, similarly to the case ofthe first piezoelectric layer 721. In this way, many crystal nucleusescan be formed in the piezoelectric precursor film 722′. In other words,the second piezoelectric layer 722, in which a number of favorablecrystal nucleuses are approximately uniformly formed, is obtained from aregion facing the lower electrode film 60A through a region facing theinsulation film 55.

Next, as shown in FIG. 13( c), a piezoelectric precursor film 723′ isformed on the second piezoelectric layer 722, to have a predeterminedthickness, which is 0.2 μm in this embodiment. Since about 0.1 μm is thethickness of the piezoelectric precursor film which is applied once,application, drying, and degreasing are carried out twice in thisembodiment to obtain a piezoelectric precursor film 723′ with a desiredthickness. Thereafter, the piezoelectric precursor film 723′ is burnedto be crystallized, forming the third piezoelectric layer 723. Asdescribed above, the steps of application, drying and degreasing thatare conducted twice to form the piezoelectric precursor film, and thestep of burning the resultant piezoelectric precursor film arerespectively carried out a plurality of times, which is four times inthis embodiment. Thus, the third to sixth piezoelectric layers 723 to726 are formed, and thereby forming the piezoelectric film 70A which isconstructed by the plurality of piezoelectric layers 721 to 726 and hasa thickness of about 1 μm.

Note that, as mentioned earlier, a relatively high rate of temperatureincrease is preferred when degreasing the piezoelectric precursor films723′ to 726′, which will be the third to sixth piezoelectric layers 723to 726. For example, in this embodiment, the rate of temperatureincrease for degreasing the piezoelectric precursor films 723′ to 726′is set to be higher than those for degreasing the piezoelectricprecursor films 721′ and 722′ which will be the first and secondpiezoelectric layers 721 and 722.

After the piezoelectric film 70A is formed in the aforementioned manner,the upper electrode film 80 is laminated as shown in FIG. 14( a). Thepiezoelectric film 70A and the upper electrode film 80 are patternedwithin a region facing each of the pressure generating chambers 12, thusforming the piezoelectric element 300 (FIG. 14( b)).

As set forth in the foregoing, in this embodiment, when forming thefirst and second piezoelectric layers 721 and 722 constructing thepiezoelectric film 70A, degreasing of the piezoelectric precursor films721′ and 722′ is conducted with a relatively low rate of temperatureincrease. When forming the rest of third to six piezoelectric layers 723to 726, degreasing of the piezoelectric precursor films 723′ to 726′ isconducted with a relatively high rate of temperature increase.Accordingly, a number of crystal nucleuses are formed in the first andsecond piezoelectric layers 721 and 722, and thus denseness andorientation of crystals are significantly improved. The crystals of therest of third to six piezoelectric layers 723 to 726 are favorablyformed continuously from the crystals of the second piezoelectric layer722, serving as nucleuses. Therefore, the film quality of thepiezoelectric film 70A is improved and also becomes approximatelyuniform over the entire piezoelectric film 70A. Thus, when a voltage isapplied to the piezoelectric element 300, favorable displacementproperties can be obtained. In addition, even if a relatively highvoltage is applied to the piezoelectric element 300, the piezoelectricfilm 70A is not broken and thereby the piezoelectric element 300 withexcellent reliability can be obtained.

Thereafter, as shown in FIG. 15( a), a metal layer made of gold (Au) isformed over the entire surface of the silicon wafer 110. The metal layeris then patterned for each of the piezoelectric elements 300 through,for example, a mask pattern (not shown) made of resist or the like, thusforming the lead electrode 90. After forming the layers in the foregoingmanner, the reservoir forming plate 30A is joined to the silicon wafer110, and then the pressure generating chamber 12 and the like is formed,as shown in FIG. 15( b). In this embodiment, anisotropic etching isperformed on the silicon wafer 110, forming each of the pressuregenerating chambers 12. Thereafter, the aforementioned nozzle plate 20and the compliance plate 40 are adhered to the silicon wafer 110 so thatthey are integrated. The silicon wafer 110 is divided into thepassage-forming substrates 10, each having a chip size. Thus, theink-jet recording head is produced.

Note that, in this embodiment the lower electrode film 60A is, thoughnot limited, continuously formed in a region corresponding to each ofthe pressure generating chambers 12 which are arrayed side by side. Itmay be possible, for example, that the lower electrode film is formed tohave a comb shape so that the lower electrode film in the region facingeach of the pressure generating chambers becomes substantiallyindependent.

Embodiment 3

FIGS. 16( a) and 16(b) are a plan view and a cross-sectional view of anink-jet recording head according to Embodiment 3.

This embodiment is an example in which metal layers are provided on avibration plate in the vicinities of edges of a piezoelectric film 70A.This construction is same as that of Embodiment 2 except provision ofthe metal layers. Specifically, as shown in FIGS. 16( a) and 16(b),metal layers 61 are provided in the vicinities of both edges of thepiezoelectric film 70A in a longitudinal direction thereof. The metalfilms 61 are formed in the same layer of the lower electrode film 60A,but are electrically disconnected from the lower electrode film 60A. Thepiezoelectric film 70A is provided, extending over a part of each metallayers 61.

Note that, in this embodiment, a metal film 61A is provided in thevicinity of the edge of the piezoelectric film 70A on the side of thelead electrode 90. The metal film 61A is also provided separately foreach of the piezoelectric elements, and the lead electrode 90 extendsover the metal layer 61A. Meanwhile, a metal layer 61B is provided inthe vicinity of the edge of the piezoelectric film 70A on the oppositeside of the lead electrode 90. The metal layer 61B is continuouslyprovided in a region corresponding to the plurality of piezoelectricelements 300.

In this construction, the piezoelectric precursor film can be heatedapproximately uniformly when burned. Thus, the piezoelectric film 70Ahaving uniform piezoelectric properties can be formed. Specifically, theinsulation film 55 made of zirconium oxide has low absorptivity ofinfrared rays in comparison with the lower electrode film 60A. Thus, theregion in which the lower electrode film 60A has not been formed hasslow increase of temperature while burning. Therefore, piezoelectricproperties may not be uniform in the region corresponding to the lowerelectrode film 60A of the piezoelectric film 70A and the other regions.However, in this embodiment, the metal layers 61A and 61B are providedin regions corresponding to both edges of the piezoelectric film 70A.Thus, the piezoelectric precursor film can be uniformly heated whileburning, thereby forming the piezoelectric film 70A having uniformpiezoelectric properties as a whole.

Another Embodiment

The embodiments of the prevent invention have been described so far, butthe construction of the present invention is not limited thereto.

For example, in the foregoing embodiments, the ink-jet recording headwas described as an example. However, the present invention may beapplied to various liquid jet heads such as: a color material jet headused for manufacturing color filters of a liquid crystal display and thelike; an electrode material jet head used for forming electrodes of anorganic EL display, a field emission display (FED) and the like; and abio-organic matter jet head used for manufacturing biochips. Further, asa matter of course, the piezoelectric element of the present inventionmay be applied not only to a liquid jet head but to any devices as longas actuators in a flexural vibration mode are used therein.

INDUSTRIAL APPLICABILITY

According to the present invention, a manufacturing method of thepiezoelectric element is provided. In the piezoelectric element, desiredand favorable crystallinity can be obtained and the uniformity of thepiezoelectric properties within the surface thereof can be improved.Thus, the piezoelectric element having the piezoelectric properties withimproved uniformity can be provided. In addition, obtained is the highlyreliable piezoelectric element in which the piezoelectric film is notbroken even if a relatively high voltage is applied thereto.

1. A piezoelectric element comprising: a lower electrode, apiezoelectric film formed on the lower electrode, and an upper electrodeformed on the piezoelectric film, wherein the piezoelectric filmincludes a lower layer portion having column crystals, and an upperlayer portion having column crystals which are continuous from thecolumn crystals in the lower layer portion and having sizes larger thanthe column crystals in the lower layer portion.
 2. The piezoelectricelement according to claim 1, wherein the lower electrode is patternedto have a predetermined shape, a first piezoelectric layer, which is alowermost layer of a plurality of piezoelectric layers constructing thepiezoelectric film, is formed only on the lower electrode, and remaininglayers of the plurality of piezoelectric layers are formed covering endfaces of the lower electrode and the first piezoelectric layer, and thefirst piezoelectric layer and a second piezoelectric layer are formeddirectly on the first piezoelectric layer to construct the lower layerportion.
 3. The piezoelectric element according to claim 2, wherein athickness of each of the first and second piezoelectric layers isthinner than that of each of the remaining piezoelectric layers.
 4. Thepiezoelectric element according to claim 2, wherein the end faces of thelower electrode and the first piezoelectric layer are inclined at apredetermined angle with respect to surfaces thereof.
 5. Thepiezoelectric element according to claim 2, wherein metallic layers,which are electrically disconnected from the lower electrode, areprovided in vicinities of edges of the piezoelectric film.
 6. Aliquid-jet head, comprising the piezoelectric element according to anyone of claims 1 to 5 as a driving source of liquid ejection.